A flash memory, an EEPROM (electrically erasable programmable read-only memory), a ferroelectric memory, and others are exemplified as nonvolatile memories. Data are stored by storing electric charges in a floating gate in the flash memory and in the EEPROM. Data are stored by using polarization inversion of a ferroelectric film in the ferroelectric memory. When these are compared, the ferroelectric memory has the advantage that resistance to radiation rays such as gamma rays, electron rays, and neutron rays is higher than that of the flash memory and the EEPROM.
However, a conventional ferroelectric memory has a problem that when a ferroelectric capacitor is miniaturized, a desired polarization charge amount is not easily secured.
Patent Literature 1: Japanese Laid-open Patent Publication No. 03-256358